Phasor fragmentation circuitry and method for processing modulated signals having non-constant envelopes

• US 20040076238A1
• Filed: 10/18/2002
• Published: 04/22/2004
• Est. Priority Date: 10/18/2002
• Status: Active Grant

• Current Assignee: Zarbana Digital Fund LLC (Intellectual Ventures LLC)
• Original Assignee: Seven Generations Energy Ltd.
• Inventors: Hobbs, Stephen R., Parker, Kevin R., DeCruvenaere, Jean-Paul R.
• Granted Patent: US 7,085,327 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2614 Peak power aspects

Abstract

An improvement for a phasor fragmentation engine and method, whereby a phasor flipping algorithm is applied when determining fragment phasors for a non-constant envelope modulation signal (e.g. OFDM). The phasor flipping algorithm avoids sharp phase transitions for the fragment phasors, which cause an increase in bandwidth, by performing a comparison of the phasor angle separation between the prior and current time samples. This comparison corresponds to a determination of whether the modulation signal V has passed near or through zero. When it is determined that the calculated phases of V_α and V_β would result in a larger angle of separation between the calculated phase of V_α (for phasor A) for the current time sample (N) and the phase of V_A for the previous time sample (N-1) than the angle of separation between the calculated phase of V_β (for phasor B) for the current time sample (N) and the phase of V_A for the previous time sample (N-1), the phase values for the phasor fragments V_α and V_β are swapped so that the phase of V_A is that of V_β (i.e. V_A=V_β) and the phase of V_B is that of V_α (i.e. V_B=V_α).

Claims

1. A phasor flipping component for use in a phasor fragmentation component of transmitter circuitry configured for digitally determining a plurality of equal amplitude fragment phasors representative of a non-constant envelope modulation signal, wherein said amplitude of said fragment phasors is a predetermined proportion of the variation of the amplitude of said modulation signal about the mean amplitude thereof, said phasor flipping component configured to perform a comparison of angle separations between preselected fragment phasors, as determined for each of prior and current time samples, and to swap the phases determined for said fragment phasors for a current time sample when said comparison identifies that said angle separation for a first said fragment phasor between said prior and current time samples changes from being less than to greater than the angle separation between a second said fragment-phasor for said current time sample and said first fragment phasor for said prior time sample.

5. A phasor flipping component according to claim 1 and configured for two equal, constant amplitude fragment phasors.

7. A phasor flipping component according to claim 5 wherein said amplitude is V_MAX/2.

8. A phasor flipping component according to claim 5 wherein said angle separation comparison is governed by the following phase limitations:

α

_N=(A, if d₁≦

d₂ (B, if d₁>

d₂ and, β

_N=(B, if d₁≦

d₂ (A, if d₁>

d₂

where, A=θ

+φ and

B=θ

−

φ

, and,

d₁=AngleSeparation (A−

α

_N-1)

d₂=AngleSeparation (B−

α

_N-1)

2. A phasor flipping component for use in a phasor fragmentation component of transmitter circuitry configured for digitally determining a plurality of equal amplitude fragment phasors representative of a non-constant envelope modulation signal, wherein said amplitude of said fragment phasors is a predetermined proportion of the variation of the amplitude of said modulation signal about the mean amplitude thereof, said phasor flipping component configured for swapping the phases determined for said fragment phasors for a current time sample when the amplitude of said modulation signal transitions near or through zero.

3. A phasor flipping component according to claim 2 and configured to determine whether the phases of fragment phasors V_α

and V_β

, as determined for fragment phasors V_A and V_B, respectively, for a current time sample (N), would result in a larger angle separation between the phase of V_α

for said current time sample and the phase of V_A for the previous time sample (N-1) than the angle separation between the phase of V_β

for the current time sample (N) and the phase of V_A for the previous time sample (N-1) and to swap the phases for V_α

and V_β

upon the occurrence of said result.

4. A phasor flipping component according to claim 3 and configured for two equal, constant amplitude fragment phasors.

6. A phasor flipping component according to claim 4 wherein said amplitude is V_MAX/2.

9. A method for determining fragment phasors for a plurality of equal amplitude fragment signals representative of a non-constant envelope modulation signal, said amplitude of said fragment signals being a predetermined proportion of the variation of the amplitude of said modulation about a mean amplitude thereof, said method comprising comparing angle separations between preselected fragment phasors, as determined for each of prior and current time samples, and swapping the phases determined for said fragment phasors for a current time sample when said comparison identifies that said angle separation for a first said fragment phasor between said prior and current time samples changes from being less than to greater than the angle separation between a second said fragment phasor for said current time sample and said first fragment phasor for said prior time sample.

14. A method according to claim 9 whereby said amplitude of said fragment signals is constant and equal to V_MAX/2.

10. A method for determining fragment phasors for a plurality of equal amplitude fragment signals representative of a non-constant envelope modulation signal, said amplitude of said fragment signals being a predetermined proportion of the variation of the amplitude of said modulation about a mean amplitude thereof, said method comprising swapping the phases determined for said fragment phasors for a current time sample when the amplitude of said modulation signal transitions near or through zero.

11. A method according to claim 10 comprising determining whether the phases of fragment phasors V_α

and V_β

, as determined for fragment phasors V_A and V_B, respectively, for a current time sample (N), would result in a larger angle separation between the phase of V_α

for said current time sample and the phase of V_A for the previous time sample (N-1) than the angle separation between the phase of V_β

for the current time sample (N) and the phase of V_A for the previous time sample (N-1), and swapping the phases for V_α

and V_β

upon the occurrence of said result.

12. A method according to claim 11 whereby two equal and constant amplitude fragment phasors are determined.

13. A method according to claim 12 whereby said amplitude of said fragment signals is V_MAX/2.

15. A method according to claim 13 whereby said angle separation comparison is governed by the following phase limitations:

α

_N=(A, if d₁≦

d₂ (B, if d₁>

d₂ and, β

_N=(B, if d₁≦

d₂ (A, if d₁>

d₂

where, A=θ

+φ and

B=θ

−

φ

, and,

d₁=AngleSeparation (A−

α

_N-1)

d₂=AngleSeparation (B−

α

_N-1)